Induction of ppp(A2'p)nA-dependent RNase in murine JLS-V9R cells during growth inhibition.

We recently reported that interferon induces the synthesis of ppp(A2'p)nA(n = 2 to greater than or equal to 4) (2-5A)-dependent RNase in the murine cell line JLS-V9R. These cells normally contain very low levels of the nuclease; after interferon treatment, however, they develop levels approaching those found in murine L or Ehrlich ascites tumor cells. Here, we report a similar increase in the nuclease levels in JLS-V9R cells during the transition from the subconfluent actively growing state to the confluent stationary phase. Levels of 2-5A synthetase increased in parallel with the nuclease. The induced levels of both the nuclease and synthetase returned to low basal amounts after trypsinization, dilution, and culturing of the cells at subconfluent densities. The addition of anti-murine interferon (alpha + beta) antibodies to the medium did not affect the induction of the nuclease nor could any interferon be detected in the culture supernatants as determined by the lack of antiviral activity. The increase in the enzymes was not, therefore, due to the spontaneous production of interferon. The induction of the nuclease during confluency preceded an inhibition of [3H]-thymidine incorporation by the cells into DNA. The regulation of the 2-5A-dependent RNase in JLS-V9R cells may, therefore, be related to the control of cell growth.